This is an exciting and dynamic time for the study of muscle and motility. The intersections of structural biology, molecular biology and biochemistry hold the promise of rapid advancements in delineating the atomic and molecular details of the myosin motor and regulation of muscle contraction. The number of actin- and tubulin-based molecular motors seems to grow each month, with the majority of their cellular functions yet to be defined. Developmental biology, genetics and molecular biology are yielding rapid advancements in the understanding of the program of muscle specification and development. The molecular basis of several muscle diseases has recently been delineated and gene therapy are being explored. Muscle also appears to hold promise as a tissue that can be used to synthesize and deliver blood-borne proteins that can be engineered to treat non-muscle diseases. This training program is based in the Pennsylvania Muscle Institute, which was formed as a cross-disciplinary research institute to promote collaborative research among muscle and cell motility researchers. The distribution of trainers in this application includes important representation in the faculty of Arts and Sciences, School of Medicine, School of Veterinary Medicine and in clinical and basic science departments. The Training Program in muscle and Motility is designed to create a premier training environment for muscle researchers. This Training Grant in Muscle Biology is the keystone of the training program. We are requesting modest support; two predoctoral trainees and two postdoctoral trainees per year. As the range of interests and expertise of the trainers listed on this grant will attest, virtually all of the important areas of current research in muscle are covered by the trainers listed on this grant. The disciplines utilized by the trainers include molecular biology, biochemistry, structural biology, developmental biology, and physiology. This provides the potential for an unparalleled training environment in the area of muscle biology. This is evidenced by the many prominent scientists around the world, who have trained in this field at the University of Pennsylvania.